What aspects of this problem [the relation of God to evil] does the Bible leave unexplained?

(a) How evil could originate in beings wholly good, as Satan and all the angels were when they were created. (b) How Satan could succeed in leading our first parents into sin, when there was no evil in their nature to which he could appeal. (c) How God could permit and foreordain evil without himself becoming responsible for its sinfulness.

These are mysteries which baffle our minds. We simply do not know the answers. Yet we dare not attempt to deny the facts. Those who attempt to solve the problem by denying these three facts only plunge into heresies which are totally destructive of Christianity. There is a point at which a reverent ignorance, rather than irreverent speculation and theorizing, becomes us.

J. G. Vos, The Westminster Larger Catechism: A Commentary, 576.